Because they are specialists, know more than you and know how to set it up without guessing and constantly making adjustments.
Everything is calculated and set accordingly.
Really?
My friend paid 4 experts to set up his bike for the TT course. 3 made it worse.
Read the manual and watch a few youtube videos, it really isn't that difficult and by trying a few settings you will learn a lot about your bike.
I set up the suspension on all my own cars and bikes, a basic skill anyone can master.
It isn't black art, it really is very simple. Only you can do it right, the guy guessing how and what road surfaces you use most is shooting from the hip.
1. Set your sag front and rear. All you need is a tape measure. 30% is a base guide
2. Set your compression low and rebound at about 1/3rd
3. Go and ride a local stretch of road you know and like. The bike will probably feel like it wallows and sinks a bit in the dips.
4. Turn up the compression a few clicks up. Try again
5. When it no longer wallows in the dips it's close, jolting on rough patches too much compression.
6. Now tweak the rebound. Too soft and it will bog down over a series of bumps, too much and it will patter. Less is the way to go.
Once you have done it a few times you can dial a bike in pretty quick as will now understand the effects. Your riding, pleasure and safety will be greatly enhanced.
Most people have their suspension set too firm, especially for UK roads. The name of the game is keeping the tires in firm contact with the tarmac, especially as speed increases.
If that's too much trouble, just check you have the settings as per the manual for your usual loaded weight.
